Phased migration from ExtremeWireless V9 to V10

I'm working on a LAB environment to find the best (or less painful) path to migrate a customer installed base to V10.

This customer is running V9.21.20 (latest code) and have about 140 legacy (non V10-supported) access points deployed, and only about 10 38xx.

With the discontinuation of thee 38xx family, now we need to create a way to keep it working and expanding, while they are working on the phased replacement of the legacy base (26xx and 36xx, indoor and outdoor).

I was thinking about moving all legacy APs to the "CONTROLLER-1" and keep it as V9, while upgrading "CONTROLLER-2" to V10 and moving all the newer APs (38xx) to it.

In the LAB I found some issues... V9.21.20 can't get synchronized with V10.41.08 (besides it shows on the V9 side's VnS-> Sync Summary as Global Config Synchronized, on the V10 side it shows as Not Synchronized, just as all other VNS, WLANS, Topologies, and everything).

The Availability and Mobility tunnels seems to be UP (at the home screen, but on logs it shows as flappling, but I need to investigate this further... all connectivity is OK and worked fine before the CONTROLLER-2 upgrade to V10).

I know we are talking about different releases, and many things can't work, but it seems that nothing works with this scenario.

Ok, we can't have HA for legacy APs and newer features can't be synchronized, but theoretically the customer could live without it while he doesn't upgrade the legacy APs, but not even the GUEST PORTAL accounts get synchronized, creating a BIG issue, forcing to create two guest accounts for the same user to make it work on both environments (by the way, the customer don't have NAC).

Most customers in this scenario are breaking their HA pairs ... leaving one running v9 and upgrading the other to v10 ... and then configuring Mobility to allow for roaming between the two.

If you currently have an HA pair ... then I believe all the Guest Accounts (if you have been syncing them between the two controllers) will still exist on both controllers after you break the pair and make them standalone.

The problem would be in maintaining those accounts moving forward. If you have to add new accounts or modify old ones in any way ... you'd have to always be doing that manually on both controllers ... to make both sides match ... or always exporting your Guest Accounts from one controller and importing them to the opposing controller periodically or something.

If this were tenable for your customer ... you would want to be on the latest version of V9 on one controller (9.21.20.0001) and the latest version of v10 on the other (10.41.08.0012).

we did several migrations with mobility groups of one V9 and one v10 controller. But we have customers with two V9 and two v10 controller (with availability)over a longer period (years), too.

If you have an XMC or an external server running e. g. python you can do the guest users sync via an little program. It's not really difficult.

Give the administrators for the guest user only access to the V9 controller and do a sync every 3 or 5 minutes. You can create and delete user on the other controllers by program. If you give the user only access to one of the controllers you can always sync in one direction and the program is more easier.

If you have more locations with APs it's a good practice to keep one site on V9 and another on V10.In that case you have the same feature set on one site and in case there is a bug (which almost never exists ;-)). It's easier to locate the issue because every AP on one side will be affected.

If you have only one controller version on one side the guest access sync is much easier because of you need to sync less often.